With increased use of facsimile as a means of exchanging information, a fax overflow feature has been increasing in popularity. FIG. 1 shows, in pictorial form, a hardware configuration which illustrates the manner in which the fax overflow feature operates. As shown in FIG. 1, private branch exchange 100 ("PBX" 100) is connected to fax server 110, fax device 120, and fax device 130. Assume that fax device 120 calls fax device 130 to deliver a fax document X. If fax device 130 is unavailable for some reason, for example, because it is already busy, broken, or so forth, PBX 100 forwards the call from fax device 120 to fax server 110; fax server 110 is designated as a fax overflow device for fax device 130.
Fax server 110: (a) answers the call forwarded from fax device 120; (b) receives fax document X; and (c) stores fax document X, for example, on disk storage unit 115. At a later time, fax server 110 calls fax device 130 and attempts to deliver fax document X. This step is repeated until delivery of fax document X to fax device 130 is successfully completed. Then, fax server 110 deletes the stored copy of fax document X from disk storage unit 115.
A problem occurs in the above which is understood as follows. Assume that fax server 110 calls fax device 130 and attempts to deliver fax document X. However, if fax device 130 is unavailable, the call is forwarded back to fax server 110. Fax server 110 then delivers fax document X to itself The previously stored copy of fax document X will be deleted and an identical, or somewhat degraded, new copy of the same fax document X is stored for delivery at a later time to fax device 130. The last few steps can be repeated many times, depending on the availability of fax device 130 and the frequency with which delivery of fax document X to fax device 130 is attempted. Note that every time fax server 110 delivers fax document X to itself it is doing unnecessary work which ties up its resources and serves no purpose since no progress is made toward achieving the ultimate goal of delivering fax document X to fax device 130. In addition, the unnecessary deliveries can cause incorrect fax logs, delivery time, and so forth to be generated by fax server 110.
The following discusses several attempts in the prior art to solve the above-identified problem. Solution 1: When fax server 110 calls fax device 130 to deliver fax document X, PBX 100 is instructed by fax server 110 not to forward the call if the destination, i.e., fax device 130, is not available. Solution 2: PBX 100 is configured not to forward a call back to the source of that call. Solution 3: Attempt to increase the availability of fax device 130. Solution 4: Increase the time period between the time at which fax server 110 receives fax document X and the time at which fax server 110 attempts to deliver fax document X to fax device 130.
Each of the prior art solutions have disadvantages. Solutions 1 and 2 are disadvantageous in that they are not universal. That is, they depend on PBX 110 to provide capabilities needed to implement the solution. This is disadvantageous in that not all PBXs allow a caller to specify that a call is not to be forwarded to an alternate destination. In addition, not all PBXs can be configured not to forward a call back to its source. Solution 2 is further disadvantageous in that there may be some situations where it may be desirable to have the call forwarded back to its source.
Solutions 3 and 4 are disadvantageous in that they do not eliminate the problem; they merely decrease the probability of its occurrence. Therefore, every time fax server 110 delivers fax document X to itself, it is doing unnecessary work which uses and ties up its resources. In addition, there is a chance that the newly stored copy of fax document X is either of equal or lesser quality than the original fax document. Further, solution 3 is not always very practical since the availability of fax device 130 cannot always be increased to the acceptable level and solution 4, under many circumstances, will cause a delay in the delivery of fax document X to fax device 130.
In light of the above, there is a need in the art for a method for preventing a facsimile overflow server from overflowing back into itself,